Special Session SS39  1 July 2024

Jets and outflows from neutron star X-ray binaries: towards a unified scenario for the ejection/accretion disc coupling in Low Mass X-ray binaries

News: Submission of contributed talks is now available. We highly encourage early-career researchers to submit. Additional details will be provided soon.

Aims and scope

Low mass X-ray binaries (LMXBs) produce some of the most powerful jets in our galaxy. These jets correspond to relativistic and collimated flows of matter originating from a region near the central compact object, which can either be a black hole (BH) or a neutron star (NS). Jets are detectable across a range of frequencies, from radio to optical (and even higher) in both BH and NS systems.

Jets play a crucial role in the accretion process in LMXBs. Thanks in large part to coordinated observing campaigns in the radio and X-ray bands, it has been realized that a connection exists between accretion and outflows in BH LMXBs. For this class of sources, compact jets are emitted during the hard states of outbursts, only to be quenched during soft states, which can be replaced by emitting hot winds at X-ray frequencies. Additionally, relativistic radio ejections can be observed during state transitions, while traces of cold optical winds can be detected in various phases of the outbursts. Whether this scenario also applies to NS LMXBs remains unclear. Moreover, theories predict jet power to be regulated by the BH spin, so NSs are an essential control sample to test that, since they have much lower spin-power.

Despite significant recent advances in the field, many questions remain unanswered. These include:

(i) Does the accretion/ejection coupling that is well established for BH LMXBs extend to NS systems?
(ii) Are hot and cold winds different outflows, or are they two facets of the same phenomenon?
(iii) Can the jet contribute up to X-ray frequencies?
(iv) Can multiwavelength polarization provide insights into the outflows in LMXBs?
(v) Are the magnetic field properties of the jets launched by NS LMXBs the same as for those launched by BH LMXBs?
(vi) How are jets formed and launched?
(vii) What are the velocities of discrete jet ejecta, compact flat-spectrum jets and disc winds?
(viii) How do neutron star jets and winds impact the ISM?

While much of the early research on these outflows has focused on BHs due to their higher brightness, recent multi-wavelength observations have revealed a new, complex phenomenology also surrounding accreting neutron stars. This allows us to study the physics and launching mechanisms of these outflows across various compact object types. Recognizing the importance of these recent discoveries, we aim to bring together experts to review these findings and discuss the directions of this exciting new field.


This Special Session consists of three blocks, each lasting 1.5 hours. Our goal is to include one review talk and 5 contributed talks in each block.
The purpose of this special session is to involve the X-ray binary community in addressing fundamental questions within the following key topics:

  • Jets in NS-XRBs: a multi-wavelength approach
  • Winds in NS-XRBs: a multi-wavelength approach
  • Jets and winds: how to bring them together

Invited speakers

  • Rob Fender (University of Oxford)
  • Teo Muñoz Darias (Instituto de Astrofísica de Canarias)
  • James H. Matthews (University of Oxford)

Scientific organisers

  • Maria Cristina Baglio (chair; INAF-OAB)
  • Federico Vincentelli (co-chair; IAC)
  • David M. Russell (NYU Abu Dhabi)
  • Maria Diaz-Trigo (ESO)
  • Sara E. Motta (INAF-OAB)
  • T. D. Russell (INAF-Palermo)


cristina.baglio @ inaf.it
vincentelli.astro @ gmail.com

Updated on Thu Feb 08 11:09:33 CET 2024